Which of the following is a straight one-dimensional figure that has two endpoints?

In geometry, a straight one-dimensional figure that has two endpoints is defined as a line segment. A line segment is the portion of a line that connects two points, known as the endpoints. It is finite in length, as it begins at one endpoint and ends at the other, making it distinct from the other types of figures listed in the choices.

A ray, while also a one-dimensional figure, starts at a single endpoint and extends infinitely in one direction, lacking a second endpoint. A line, on the other hand, extends infinitely in both directions and therefore does not have endpoints at all. A polygon is a two-dimensional shape formed by a closed chain of line segments, and it cannot be described as having only two endpoints since it consists of multiple segments and vertices.

Thus, the unique characteristics of the line segment make it the correct choice in this context.